T@B 320S Air Conditioner Hot Weather Testing

CincyKid

Out of curiosity I completed a driveway test of my 320S AC System today.  The test started at 2:42 pm since it was now a hot day (87F on my home thermometer in the shade on the back of my house, 92F per Alexa for my area).  I used the digital thermometer provided by NuCamp that I had mounted by the shower door about 6" from the curved part of the ceiling.  That area is usually about the hottest place for hot air since hot air rises to that spot and the AC cold air does not blow directly into that area.  As the test progressed I put another portable digital thermometer on the kitchen counter since it is lower in the living space and I wanted to see how it compared to the ceiling area.

At the start of the test the temperature inside the trailer (no open windows or vents) was a very toasty 121.3F.  I turned the Danby AC unit on at the max cooling setting and then took readings regularly for the next ~6 hours monitoring the drop in the interior temperature.  It took hours but eventually the temperature became bearable.  For the first two hours  the trailer was exposed to direct sunshine until about 5 pm when shadows from my trees started to shade the outside of the trailer, although the outside air temperature was still running about 90-92F.  About 5 pm I turned on the AC cabinet fan to see if that changed the slope of the temperature reduction since that 'computer fan' in the cabinet is supposed to help get more outside cooling air across the AC coils.  Then at 6:47 pm I magnetically attached two air deflectors to the outside of the trailer (photo below) to see if it would reduce AC exhaust air from being sucked back into the AC to blow across the coils to see if the rate of cooling improved.  Here is the plot, and I will provide my conclusions below.

Results:

1) the outside air temperature ranged from 85-92F during the test depending on if I used the value provided by Alexa for my city (purple squares), or the thermometer in my shaded backyard (green triangles).

2) the Danby unit was slow, but like the turtle in the race against the hare dropped the interior temperature from 121F to 75F over the period of the test (the bold red line with diamond symbols), and was still lowering the temperature when I ended the test - so if you know it is going to be a hot day turn on the AC unit before it gets hot and it will likely hold a cool enough temperature.

3) I did not see a significant change in the slope in cooling by turning on the 'computer fan' inside the AC unit cabinet, perhaps it would speed things up a bit?

4) Similarly I did not see a significant change in the cooling slope with the outside deflectors attached to the outside of the exhaust area (see photo below); the idea being that the hot exhaust air comes out the center of the grill and replacement air is pulled in on each side of the grill.  The deflectors would help keep those flows separate.

5) there was no wind during the test so I don't know if the deflectors would help on a windy day - I have to point out that my deflectors did not sit flush with the exhaust louvers owing to the height of the magnets I glued on to hold them in place.

6) the temperature on the kitchen counter mirrored the one up near the ceiling within 1-2 degrees throughout the cool down.

pthomas745

Nicely done.  I'm a sucker for charts and graphs.

Do you think trying to use the Fantastic Fan to exhaust  hot air out of the trailer would improve the outcome? 

broderius

For those with AC issues, try starting the AC earlier in the day so it doesn't have to work so hard at keeping the temperature down. 

CincyKid

@pthomas745: I am pretty sure the Fantastic Fan would do a good job of removing the hot air above the outside air temperature, that is, the 122F AIR would have dropped to 92F fairly quickly, however, the walls and solid materials would still give off heat for some time.  For my test I wanted to see if the AC system would fall short of an acceptable value (stalling at an unacceptable value) or if it would get ahead of the built up heat in the trailer.  Fortunately as the plot shows it kept getting cooler and cooler.  So, for example, if you were leaving your trailer in the morning with the weather forecast of a really hot day, with the AC on, it should be acceptably cool inside if you come back hours later.  If you had the Fan on it would continue to pull in hotter air as the day got warmer.  So the test showed the AC has sufficient cooling power, but you have to anticipate starting it to avoid a long cool down period.

ColleenD2

This is wonderful, thank you.

Ratkity

Scientist here. You did a great job of seeing how well the AC cooled under typical conditions over 5 hours; however, you added two extra variables to your experiment which may have confounded your graph, the deflectors and the computer fan. 

To tease out the differences of those two variables, Do four days of similar hot temps starting at a set time. 1 - Graph of heat dissipation over time with the AC only. Day 2, same graph with AC plus AC fan. Day 3, AC plus Deflectors.  Those are your controls when you use two variable. Your last day (Day 4) will be defectors + fan. If you want to add a 3rd variable (fantastic fan), the controls (comparators) get a little more complicated OR you can use the fantastic fan before you start the experiment for 30 minutes to see if the temps come down rapidly (rem to crack open windows). Then start your experiments. This way, the shadows, the natural temperature fall in the evening will not be confounding factors in your experiments, but just part of the neutral conditions.

Your graph opened eyes to people that helping the AC cool will with all available tools (including fantastic fan) is most likely the absolute best way to help the little unit do its job! People may not want to spend 5 hours outside to get their little unit cooled off!

Just a question. my deflectors are held on by industrial velcro strips. I had trouble with the magnets. Are the magnets holding the deflectors fairly far away from the fins or is that a trick of the camera? If the magnets are preventing the deflectors from getting close to the fins, they might not be as efficient as they could be. Again, the picture may be a camera angle issue.

GREAT JOB!!! Very much an eye opener.

Sharon_is_SAM

@CincyKid, you can add some foam to fill the space between the grill and deflector.  

jkjenn

@CincyKid from my own experience, the A/C could keep up until it started to get above 95, outside, by lunch time. But, I found that it cooled very quickly after the sun went down.

I have been considering getting some shade cloth for the T@b for those super hot days. Similar to what some of our AZ T@b owners have done with their shelters.

Also, if you can use some type of awning and window awnings, it can help. I have been thinking about cutting out reflectix to fit into the windows for super hot weather.

CincyKid

@Ratkity I suppose if I did your suggested testing I could put all of the data into Minitab and perform a multiple variable regression analysis to confirm if the other variables are significant, but the test successfully proved what I wanted to know - if the continual heat rejection to the outside world would stall before reaching an acceptable temperature or continue to reduce the inside temperature.   Another variable I kept track of was if the roof of the trailer was in direct sun or in the shade - that has to be another significant variable.

I was a certified Black Belt at my company prior to retirement so I get where you are coming from in regards to variables.  There is about a 0.5" gap between the grill louvers and the deflector body - my next step will be to do smoke test tracking to see if that gap causes hot air to return to the AC coils or if only 'cool' outside air is sucked in.   If yes I might consider filling in those 4 gaps.  BTW, the name for my 320S is MiniT@B.

Lil_Lucy

CincyKid said:

I was a certified Black Belt at my company prior to retirement 

I’m a retired Quality Engineer so I’m assuming you’re referring to being a Certified Black Belt in the field of quality and that you didn’t go around beating up on fellow employees. lol.

Sharon_is_SAM

This is why we don’t need cable - entertainment and an education!

DougH

Hey, I retired to get away from six sigma / design of experiments debates!  

CincyKid

I was actually a Program Manager for gas turbine development, but one that was six-sigma trained to help make sure that good designs and good decisions were being made.  I really believed in power of statistics.  And I didn't go around beating up on fellow employees!

BrianZ

Nicely done, @CincyKid!
It seems like ours cools faster than that, but then ours probably never got that hot inside yet.  We do keep windows cracked & roof vent open.
Good lesson though to start cooling hours in advance, just like the frig.

Ratkity

The MiniT@B sounds like it has a great engineer able to handle most anything that is thrown its way. 

I'm still full-time working and just seeing "six sigma" words made my tummy jump in a bad way

"Think of MiniT@B, think of MiniT@B!!!" The mantra made me relax. Phew!

I hope you took my geeky message in the spirit in which it was intended, Big Bang geekness and not criticism!!!! My sister calls me a female Sheldon... apologies to those who don't watch that sitcom. It's a hoot! 

Seriously, you did a great job and even made a graph! I am impressed.

CincyKid

NO issues  I belong to a kayaking club where personality bashing is de riguer and expected.  Being a geek these days is kind of a red badge of courage!

Ratkity

OMG.. I just re-read. A smoke test!! hehehehehehe. I love it. Keep those experiments coming! May I suggest smoke from Sandalwood incense? hehe

rkj__

Excellent.  Thanks for gathering and presenting the data. 

jkjenn

I had the chance to eat lunch with @Ratkity. Truly one of the most interesting people I have ever had the pleasure of meeting!

hymie

@CincyKid Nothing like good data to understand how something works! We used hdxl foam "fingers" to ensure that the cold and hot air don't mix. Credit to Joseph langrek (off FB tab post) for the basic cover  concept (louvers are my add based on @Dalehelman concept of separating the air flow).

Ratkity

jkjenn said:

I had the chance to eat lunch with @Ratkity. Truly one of the most interesting people I have ever had the pleasure of meeting!

Jenn and I were just going to say Hello for a little while since I was passing her way. We spoke for hours!! What a great time! We geeked solar, tow vehicles, photography, science (that was me, can't help it), and then every other topic under the sun. What a privilege! T@B people are the bestest. We could have visited for a lot more time, but I was needing to try to avoid rush hour traffic. Good memory!

Sharon_is_SAM

@hymie, I am confused as to why you placed the foam on the outside edges as the cool air enters in the middle, no?

jkjenn

@Sam looks like fingers are keep louvers wide open?

Sharon_is_SAM

Nevermind.  I thought the picture with the foam was the outside edge of the grill.  It is actually the same place where Dale places the foam.  To fill the space between the A/C unit and the screening to prevent hot vs fresh air from mixing.

CincyKid

After I get some incense I will perform a smoke test to see if air naturally wants to intermix in that area.  However, I bought some round foam to cut and shove into those spaces for certainty.

dsfdogs

Interesting data! Not a Scientist, just analytical. I did my own test this weekend camping in SE Washington. Parked in full sun. Too windy for my umbrella to help shade one side, so I pulled the window shade on the sunny side and had window awnings on the other two windows. All windows in vent position. At first I had the Fantastic fan on, but because the air conditioning vent blows at ceiling level it seemed to just suck out the cold air, so I closed it.

Starting inside temp at 85*. I had my nuCamp supplied thermometer on the table. Per the manual, I slowly turned the A/C on, first to fan, then first position A/C. I started the temp dial at 1 and slowly turned up every few minutes. It was cool but the cooling didn't seem to kick on until "8" and I could hear it kick on. (The second day it kicked on about 5). From that point on, it took an hour to cool down to 68* and we were happy campers. (I never turned the A/C fan to the high position or it probably would have cooled faster).

I was also pleased to see drips from the drainage tube outside. 

hymie

@SAM You are right. The foam is at the pivot of the flaps. This is just a different version of Dales' method of keeping the airflow separate. I had already decided to make a version of Josephs' cover so it seemed like a no brainer to integrate Dales' ideas.

DougH

Today I swapped out the 5000BTU Danby for a 6000BTU LG LW6017R ($189).  Not Energy Star, but close to the Danby's dimensions.  A little surgery on box and front face. Have A/C fan on to pull air from the roof over the top and sides of A/C. Have alum foil and duct tape to keep all exhaust headed outside on top and two sides. LG will cool for five minutes when set to 60F, but then take a break for a while before starting back up.  Doubt computer fan is keeping up with exhaust flow so maybe hot air is being sucked from the exhaust down through the drip pan and back into the inlet on the external side, heat soaking the unit (?) and causing the condenser to take a break.  I will let it run a few hours and see if it drops to the 70s.  If not, I'll try making a complete seal from the exhaust to the outside, and leave a gap in my foam insulation to let some air from the cabin get to the exhaust side inlets.

CincyKid

Yesterday I completed a short ~1 hour test to see how quickly the Fantastic Fan would cool off a hot trailer where the 320S was completely closed up and registering 116.8F inside up near the ceiling, and the outside temperature was reported as 92F by Alexa for my area.  One of the readers above wondered if the Fantastic Fan would have helped reduce the temperature more quickly than the AC unit.  That is, would somewhat cooler ambient air cool the inside faster that just using the AC Only?

After measuring how hot it was with everything closed up I opened one side window at least 6 inches at the bottom, and turned the Fantastic Fan to its highest setting with the vent for the fan opened as far as it could go.  I should note that for this test and the one yesterday my trailer was oriented East-West with the sun beating down on the roof surface which I believe to be a very significant variable.  Here is a plot of the rate of cooling with my conclusions below.

Conclusions: The cooldown was much slower than I expected since it only lowered the ceiling air temperature by 10.8F in the first 45 minutes.  During the prior day's test the Danby AC unit lowered the ceiling air temperature by about 21F in the first 45 minutes (although the trailer was hotter at the start).  For both days the outside air temperature was about 92F during the first 45 minutes of both tests.  My conclusion would have to be that using the AC Unit will cooldown a very hot trailer faster than using the Fantastic Fan first.

I also did a smoke test today to check for the air flow patterns around the two 90 degree exhaust air deflectors, primarily to see if some of the hot exhaust air might get sucked back into the two side inflow areas.  My first attempt was using a fog machine that I use for Halloween here.  I found that it put out some much fog that it was difficult to see the air flow pattern.  Then using another suggestion from above, incense sticks, I was able to see the smoke pattern more clearly (photos below). 

The answer was 'yes' some of the air near the hot exhaust is likely getting sucked back into the cooling air, giving value to putting in blocking material to prevent that recirculation, per the photos provided above by @hymie.

Photo showing smoke entering into side of the vent as cooling air (desired)

Photo showing smoke from the exhaust area getting sucked into the cooling area (undesired).

I am running a final test today doing a 12 hour AC run starting at 8 am in the morning to see how much benefit there is to starting the AC unit early in the day - will it hold off hot temperatures in the trailer?  Stay tuned for the exciting answer.....  All of these tests are of value to me since I am going to be camping next week for 4 days near the Cuyahoga Valley National Park and it is likely to be hot some of those days.

Sharon_is_SAM

@CincyKid, lucky for you, the forecasted high temp in Cleveland over the next 4 days is 76 F.

pthomas745

I think the gist of my question about the Fantastic Fan was:  would the trailer cool faster if the Fantastic Fan was drawing hot air out of the camper when the AC was first started?  I realize that eventually you would be pulling cold air out of the top of the camper.  I always think of "air as a fluid," and think that trying to shove cool air into a trailer already filled with hot air would take the AC longer to cool.

PS:  The good news is, the Fantastic Fan did get the trailer down to 105!  Woo-hoo!